Sennheiser RS170 - HDR170

Hi
I'm after some advice. I've got a pair of RS170 headphones with the transmitter. I was thinking of buying the RS160 set up so that 1. My wife could listen on my RS170 set up and 2. We could use the RS160 transmittter to listen when we go camping.
I have read in your article on the HDR170/RS170
' The transmitter, like the headset, runs off two AAA batteries allowing you to hit the streets with wireless tunes'.
I've looked at my RS170 transmitter and it appears to be mains. Can you please clear this issue?
Thanks